The invention relates to an electric conductor with a cavity forming a pipeline which is arranged in the conductor cross section and extends along the longitudinal axis of the conductor; this cavity holds a refrigerating agent, flowing through the conductor under pressure, and conducting electric currents of high density while the conducting body is heated.
Electric conductors of this kind are used, e.g., as inductors in high or medium frequency induction tempering installations and, generally, have in these instances a rectangular cross section with a cavity also having a rectangular cross section with smooth walls to guide the cooling water flow through the conductor. The arrangement of the conductor itself is in these cases in such shapes as will serve as inner or outer inductors, with one or several windings in the form of a fork, for instance, in the form of a flat spiral or cylindrical spiral, in flat meander form, etc.
Independently of the geometric arrangement of the conductor, it can be noticed in case of high thermal loads of such conductors that the walls of the piping for the refrigerating agent are covered, after more or less long periods of time, with deposits, of lime for instance, or other impurities of the refrigerating agent which obstruct the flow of the refrigerating agent and thus cause a further increase of the specific thermal load of the conductor.
It is, therefore, known to only use treated water for the cooling. However, under practical operational conditions the quality of the cooling water or of other liquids is not the same in all plants and does not always meet the necessary requirements. Therefore, the conductors are often destroyed after a rather short period of time.
Is is the object of this invention to increase this period of time for thermally highly loaded conductors of the above mentioned kind by decreasing the deposits on the walls of their piping for refrigerating agents.
By the same token, the problem of increasing the current density produced in the conductor without changing this period of time is solved.
In accordance with the invention, this problem, with respect to electric conductors of the kind as described above, is solved in such a way that the surface of the walls of the cavity in the conductor, which is in contact with the refrigerating agent, has a non-smooth, undulating profile showing slots, grooves, furrows, etc.
The furrows in the walls, which preferably should have the form of an isosceles triangle, can also be trapezoidal, rectangular of dovetailed or have other configurations, whereby the raised parts of the walls can either have acute-angled, obtuse-angled or rounded edges.
The furrows should preferably run in the direction of the flow of the liquid refrigerating agent.
Due to the furrowed form of the surface of the piping for the refrigerating agent, the heat contact between the refrigerated agent and the enlarged surface of the electric conductor is increased and thus the heat transfer from the conductor into the refrigerated agent is improved. The specific thermal surface load of the conductor is therefore reduced. At the same time, the speed of deposits of foreign matter in the refrigerating agent on the surface of the piping for the refrigerating agent is reduced and the operational period of time of the conductor is increased.
Deviating from the arrangements of the furrows in the direction of the flow of the refrigerating agent, the arrangement could also be such that the furrows, slots or grooves in the profile of the conductor show an inclination against the direction of the flow of the refrigerating agent or show an inclination against the direction of the refrigerating agent and in the direction of the flow. In this instance, the arrangement can be made in such a way that the furrows of the profile have little depth and small distances between each other, with a relatively great number of furrows in the walls of the elcgric conductor. Here it would be appropriate that the slots, grooves or rills have a distance from each other in the dimensions of millimeters and a depth which is about similar to the distance.